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div.relative{
    position: "relative";
    width: 400px;
    height: 200px;
    border: 3px solid#73AD21;
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div.absolute{
    position: absolute;
    top:80px;
    right:0;
    width: 200px;
    height: 100px;
    border:3px solid #73AD21;
}
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    <h1>position: absolute;</h1>
    <p>设置 position: absolute; 的元素会相对于最近的定位祖先进行定位（而不是相对于视口进行定位，比如 fixed）：</p>
    <div class="relative">这个 div 元素设置 position: relative;
    <div class="absolute">这个 div 元素设置 position: absolute;</div>
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